Phthalic anhydride, 1, 2, 4-phthalic anhydride, also known as partial anhydride. The molecular formula is C9H4O5. Appearance of white sheet, melting point, 164-166. Boiling point 240-245, soluble in hot water and acetone, 2-J ketone, dimethyl formamide, ethyl acetate, cyclohexanone. Soluble in anhydrous ethanol and reaction, slightly soluble in carbon tetracloride, toluene.

Phthalic anhydride used for manufacturing polyester resin and polyimide resin, water-soluble polyester resin, water-soluble polyurethane resin, plasticizer and water-soluble amino alkyd resin, epoxy resin curing agent and advanced aviation lubricating oil, power capacitor impregnation oil, particle binder, sizing agent, smoke reducing agent, instantaneous binder and TOTM, etc.